This invention concerns an apparatus for the partial treatment of elongated articles by current intensive glow discharge with a receptacle and a direct current source, which can be connected with the article and the receptacle.
In the treatment of articles by current intensive glow discharge, for example, for the purpose of nitriding, carbonitriding, carburizing, metallizing, annealing or the like, the articles are arranged in a receptacle which is evacuated, whereupon the articles are heated to the treatment temperature indirectly by external heating or directly by glow discharge and are then treated for a predetermined time period, possibly by the use of a treatment gas, which flows through the receptacle. If certain areas of an article, which should be nitrided, are to remain soft, these areas are covered by sheetmetal or the like or coated with a copper paste, so that nitride hardening will not take place in these areas. However, if elongated articles are to be treated only partly, for example, only the thread of pipes of a drill pipe, the insertion of the entire pipe into a correspondingly large receptacle, as well as the application of a protection for the areas of the article, which should not be treated, would result in a disproportionately high energy consumption because the entire article is heated to the treatment temperature, while only a small part is to be treated. Furthermore, a relatively large amount of labor would be required for the application of the protection and a very large receptacle would be required, with a correspondingly extensive high power current supply and appropriately designed vacuum pumps. On the basis of the large volume of the receptacle, the consumption of gas would be correspondingly large and a strong suspension for the article would also be required.